With a hearing aid an input signal is picked up by means of an input converter and converted into an electrical input signal. Usually at least one microphone which picks up an acoustic input signal serves as an input converter. Modern hearing aids frequently comprise a microphone system with a number of microphones so as to achieve reception which depends on the direction of incidence of acoustic signals, a directional characteristic. The input converter can however also include a telephone loop or an antenna to pick up electromagnetic input signals. The input signals converted by the input converter into electrical input signals are routed to a signal processing unit for further processing and amplification. The further processing and amplification is undertaken to compensate for the individual loss of hearing of a hearing aid wearer and is generally a function of the signal frequency. The signal processing unit emits an electrical output signal which is fed via an output converter to the hearing of the hearing aid wearer so that the wearer perceives the output signal as an acoustic signal. Earpieces which generate an acoustic output signal are usually used as output converters. However output converters to generate mechanical oscillations are also known, which directly excite specific parts of the hearing into oscillation, for example the small bones in the ear. Furthermore output converters are known which stimulate the nerve cells of the hearing directly.
A hearing aid is known from EP 0 064 042 B1 with a microphone, a signal processing unit and an earpiece, in which different parameters can be stored in a memory for adapting the signal processing unit to different hearing situations. This means that, for different hearing situations, the hearing aid can be equipped with different hearing programs, between which manual switchover is possible.
A hearing aid is known from U.S. Pat. No. 5,604,812 which features a signal analysis unit for automatic switchover between different hearing programs, said unit detecting the current hearing situation and selecting a suitable hearing program.
A hearing aid with a wired remote control is known from U.S. Pat. No. 5,721,783. The remote control can be connected to a wide variety of sensors and peripheral units to provide solicited and unsolicited information. For example information about the position of a user can be communicated by specially embodied transmitters at specific points in a senior citizens' home or a self-contained, inertial navigation system worn by the user, with gyroscope, acceleration measurement device or compass, or a GPS (Global Positioning System) receiver can be used.
A hearing aid is known from DE 100 48 341 C1 which, to automatically select a hearing program, detects whether it is in the immediate vicinity of an external transmitter. The transmitter creates a transmitter-specific signal, so that different transmitters can be assigned.
In “Retooling the Global Positioning System”, Scientific American, May 2004, P. Engel describes how GPS functions and of discusses developments of satellite-assisted positioning systems. D-GPS (Differential GPS) for example allows positions to be accurately determined down to 30 to 50 cm as well as positioning within buildings under certain circumstances.